title: Detection of B-cell populations with monotypic light chain expression in cerebrospinal fluid specimens from patients with multiple sclerosis by polychromatic flow cytometry.
abstract: BACKGROUND
  Flow cytometric immunophenotyping is an established method for the detection of occult leptomeningeal disease in patients with aggressive B-cell non-Hodgkin lymphoma, and is increasingly being used in the evaluation of patients without an established diagnosis of lymphoma who present with signs and/or symptoms referable to the central nervous system. However, the specificity of flow cytometric immunophenotyping in the identification of monoclonal B-cell populations in cerebrospinal fluid (CSF) has not been systematically evaluated.
  
  
  METHODS
  We searched a consecutive series of CSF specimens submitted to our laboratory for polychromatic (8-color) flow cytometric immunophenotyping between June, 2010 and December, 2012 for cases in which a B-cell population with monotypic immunoglobulin light chain expression was detected in patients without clinical or radiographic evidence of lymphoma.
  
  
  RESULTS
  A B-cell population with monotypic light chain expression was identified in CSF specimens from three patients whose subsequent clinical and radiologic evaluation provided no evidence for lymphoma. In all three patients, a diagnosis of multiple sclerosis was ultimately rendered upon completion of the clinical evaluation.
  
  
  CONCLUSIONS
  We conclude that the detection of a B-cell population with monotypic light chain expression in CSF by polychromatic flow cytometry is not diagnostic of occult leptomeningeal involvement by a B-cell non-Hodgkin lymphoma. Moreover, these findings suggest that monotypic B-cell populations detectable by polychromatic flow cytometry may be prevalent in patients with multiple sclerosis, and highlight the importance of clinicopathologic correlation in this application of polychromatic flow cytometry.
authors.affiliation: Department of Pathology & Laboratory Medicine, Hartford Hospital, Hartford, Connecticut.
authors.forename: Poopak
authors.initials: P
authors.lastname: Vafaii
authors.forename: Joseph A
authors.initials: JA
authors.lastname: DiGiuseppe
mesh_terms: D000328:Adult; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D002555:Cerebrospinal Fluid / Q000166:cytology* / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000096:biosynthesis* / Q000276:immunology; D016130:Immunophenotyping; D008297:Male; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000276:immunology; D055815:Young Adult
chemical_list: D007147:Immunoglobulin Light Chains
keywords: B cells; cerebrospinal fluid; flow cytometry; monoclonal; multiple sclerosis; polychromatic